Recent years have brought on a new breed of HMDs. They have high resolution, are daylight readable, and some even
have color. While these are all welcomed advances to the field we must remember to review our history. Here we review
some the of the research from years past that was done before these advances and discuss them so as to make sure the
past is not forgotten and mistakes are not repeated.

With the introduction of helmet-mounted displays (HMD) into modern aircraft, there is a desire on the part of pilot
trainees to achieve a "look and feel" for the simulation environment similar to the real flight hardware. Given this
requirement for high fidelity, it may be necessary to configure - or to perhaps re-configure - the HMD for a short
conjugate viewing distance and to do so without causing eye strain or other adverse physiological effects. This paper will
survey the human factors literature and provide an analysis on the visual construct issues of focus and vergence which -
if not properly configured for the short conjugate simulator - could cause adverse effects, which can negatively affect
training.

Designers, researchers, and users of binocular stereoscopic head- or helmet-mounted displays (HMDs) face the tricky
issue of what imagery to present in their particular displays, and how to do so effectively. Stereoscopic imagery must
often be created in-house with a 3D graphics program or from within a 3D virtual environment, or stereoscopic
photos/videos must be carefully captured, perhaps for relaying to an operator in a teleoperative system. In such
situations, the question arises as to what camera separation (real or virtual) is appropriate or desirable for end-users and
operators. We review some of the relevant literature regarding the question of stereo pair camera separation using deskmounted
or larger scale stereoscopic displays, and employ our findings to potential HMD applications, including
command & control, teleoperation, information and scientific visualization, and entertainment.

A dichoptic HMD vision system can provide an expansive and highly detailed visual experience by presenting a
large FOV, lower quality image to one eye and a small FOV, higher quality image to the other. We compared a
benchtop dichoptic vision system (DiVS) to a reference binocular system (RBS) using both subjective ratings and a
performance test. Subjective ratings were directed at questions involving image quality, viewing comfort and
presence or immersion. The performance test required observers to scan the scene to locate a target and then make
an identification. Response times were collected for each component of this task. Target acquisition times were
found to be much shorter for the DiVS condition while target identification times were longer. Total time to acquire
and identify a target was found to be significantly shorter for a dichoptic system.

Non see-through, monocular helmet mounted displays (HMDs) provide warfighters with unprecedented amounts of
information at a glance. The US Air Force recognizes their usefulness, and has included such an HMD as part of a kit for
ground-based, Battlefield Airmen. Despite their many advantages, non see-through HMDs occlude a large portion of the
visual field when worn as designed, directly in front of the eye. To address this limitation, operators have chosen to wear
it just above the cheek, angled up toward the eye. However, wearing the HMD in this position exposes the display to
glare, causing a potential viewing problem. In order to address this problem, we tested several film and HMD hood
applications for their effect on glare. The first experiment objectively examined the amount of light reflected off the
display with each application in a controlled environment. The second experiment used human participants to
subjectively evaluate display readability/legibility with each film and HMD hood covering under normal office lighting
and under a simulated sunlight condition. In this test paradigm, participants had to correctly identify different icons on a
map and different words on a white background. Our results indicate that though some applications do reduce glare, they
do not significantly improve the HMD's readability/legibility compared with an uncovered screen. This suggests that
these post-production modifications will not completely solve this problem and underscores the importance of
employing a user-centered approach early in the design cycle to determine an operator's use-case before manufacturing
an HMD for a particular user community.

In virtual reality (VR) circles a "cave" is a 3-6 sided box with displays on each side. It has for many years sufficed as
the "immersive" portion of VR mostly due to the insufficient head-mounted displays (HMDs) in the domain. However,
current HMDs rival many caves and indeed are taking over. Here we discuss the pros and cons of this advent as well as
human factors issues related to VR and the use of HMDs.

A method to enhance the legibility of FLIR (Forward-Looking Infra Red) images was invented and evaluated by flight
test. The method intends to avoid image saturation when a pilot is looking for low temperature objects of interest in an
image dominated by high temperature areas, such as searching for objects on a cooler land area in an image mostly filled
with a warmer sea area. The method utilizes a 2D mask generated from 3D object of interest data, and overlays the raw
image. The effectiveness of the method was evaluated by flight tests in which the processed image was presented on a
HMD (Helmet Mounted Display). The flight tests confirmed the enhanced image legibility brought by the method.

This paper presents a method for computing position and attitude of an instrument attached to the human body such as a
handheld or head-mounted video camera. The system uses two Inertial Measurement Units (IMUs). One IMU is part of
our earlier-developed Personal Dead-Reckoning (PDR) system, which tracks the position and heading of a walking person
relative to a known starting position. The other IMU is rigidly attached to the handheld or head-mounted instrument.
Our existing PDR system is substantially more accurate than conventional IMU-based systems because the IMU is
mounted on the foot of the user where error correction techniques can be applied that are unavailable for IMUs mounted
anywhere else on the body. However, if the walker is waving a handheld or head-mounted instrument, the position and
attitude of the instrument is not known. Equipping the instrument with an additional IMU is by itself an unsatisfactory
solution because that IMU is subject to accelerometer and gyro drift, which, unlike in the case of the foot-mounted IMU,
cannot be corrected and cause unbounded position and heading errors. Our approach uses transfer alignment techniques
and takes advantage of the fact that the handheld IMU moves with the walker. This constraint is used to bound and correct
errors by a Kalman filter. The paper explains our method and presents extensive experimental results. The results
show up to a five-fold reduction in heading errors for the handheld IMU.

The US Army and eMagin Corporation established a Cooperative Research and Development Agreement (CRADA) to
characterize the ongoing improvements in the lifetime of OLED displays. This CRADA also called for the evaluation of
OLED performance as the need arises, especially when new products are developed or when a previously untested
parameter needs to be understood. In 2006, eMagin Corporation developed long-life OLED-XL devices for use in their
AMOLED microdisplays for head-worn applications. Through research and development programs from 2007 to 2010
with the US Government, eMagin made additional improvements in OLED life and developed the first SXGA (1280 X
1024 triad pixels) OLED microdisplay. US Army RDECOM CERDEC NVESD conducted life and performance tests
on these displays, publishing results at the 2007, 2008, 2009, and 2010 SPIE Defense and Security Symposia1,2,3,4. Life
and performance tests have continued through 2010, and this data will be presented along with a recap of previous data.
This should result in a better understanding of the applicability of AMOLEDs in military and commercial head mounted
systems: where good fits are made, and where further development might be desirable.

Spatial noise in imaging systems has been characterized and its impact on image quality metrics has been addressed
primarily with respect to the introduction of this noise at the sensor component. However, sensor fixed pattern noise is
not the only source of fixed pattern noise in an imaging system. Display fixed pattern noise cannot be easily mitigated
in processing and, therefore, must be addressed. In this paper, a thorough examination of the amount and the effect of
display fixed pattern noise is presented. The specific manifestation of display fixed pattern noise is dependent upon the
display technology. Utilizing a calibrated camera, US Army RDECOM CERDEC NVESD has developed a microdisplay
(μdisplay) spatial noise data collection capability. Noise and signal power spectra were used to characterize the
display signal to noise ratio (SNR) as a function of spatial frequency analogous to the minimum resolvable temperature
difference (MRTD) of a thermal sensor. The goal of this study is to establish a measurement technique to characterize
μdisplay limiting performance to assist in proper imaging system specification.

Gentex Corporation presents experience with the first binocular implementation of its Scorpion Helmet
Mounted Display (HMD) System. Gentex has a working prototype for a binocular version of Scorpion,
using two Scorpion PD-14 displays mounted on a single helmet. The prototype has excellent
characteristics for a binocular helmet. The displays' optical characteristics make them easy to harmonize
and comfortable to use without eyestrain. The displays are light enough not to unduly affect the weight of
the helmet or center of gravity. Harmonization, which has been a significant problem with other binocular
display systems, is easy to achieve, and once achieved remains fixed without issue.

SA Photonics has developed (with support from the Air Force Research Lab, the US Army and Vision Systems
International) an innovative wide field of view digital night vision head mounted display (HMD). This HMD has an 80
degree field of view to greatly improve operator situational awareness. By using creating an all-digital system, we
provide the capability to enhance and record night vision imagery, overlay symbology, and inset video from remote
sensors, either mounted on the aircraft or on UAVs. This HMD has been designed with maximum pilot utility in mind,
and is easily stowable without impacting center of gravity or maneuverability of the pilot's head within the cockpit.
Because the sensors are digital, they can be located right above the pilot's eyes removing any hyperstereoopsis.

See-through near-to-eye displays offer an opportunity to present visual information laid on top of the view of the real
world. The information presented can be used to augment or annotate the scene the user sees. Microvision has
developed a see-through, full-color, daylight-readable, monocular display in a goggle form factor. The image source for
the display is a Pico Display Engine (PDE) that uses modulated red, green, and blue lasers reflecting off a MEMS based
bi-axial scanning mirror to create an image. This image is relayed to the eye through a pupil-expanding substrateguiding
optic. The low Lagrange invariant laser-based display engine is an excellent match for the substrate guided
optics for presenting the user with an infinite conjugate image. This paper discusses design considerations and
performance characteristics of the eyewear display.

Previous foveal/peripheral display systems have typically combined the foveal and peripheral views optically, in a single
eye, in order to provide simultaneously both high resolution and wide field of view from a limited number of pixels.
While quite effective, this approach can lead to cumbersome optical designs that are not well suited to head-mounted
displays. A simpler approach may be possible in the form of a dichoptic vision system, wherein each eye receives a
different field of view (FOV) of the same scene, at different resolutions. One eye would be presented with highresolution
narrow-FOV foveal imagery, while the other would receive a much wider peripheral FOV. Binocular overlap
in the central region would provide some degree of stereoscopic depth perception. It remains to be determined, however,
if such a system would be acceptable to users, or if binocular rivalry or other adverse side-effects would degrade visual
task performance compared to conventional head-mounted binocular displays. In this paper, we describe a preliminary
dichoptic foveal/peripheral vision system and suggest methods by which its usability and performance can be assessed.
This effort was funded by the U.S. Air Force Research Laboratory Human Performance Wing under SBIR Topic
AF093-018.

The operating concepts emerging under the Next Generation air transportation system (NextGen) require new technology
and procedures - not only on the ground-side - but also on the flight deck. Flight deck display and decision support
technologies are specifically targeted to overcome aircraft safety barriers that might otherwise constrain the full
realization of NextGen. One such technology is the very lightweight, unobtrusive head-worn display (HWD). HWDs
with an integrated head-tracking system are being researched as they offer significant potential benefit under emerging
NextGen operational concepts. Two areas of benefit for NextGen are defined. First, the HWD may be designed to be
equivalent to the Head-Up Display (HUD) using Virtual HUD concepts. As such, these operational credits may be
provided to significantly more aircraft for which HUD installation is neither practical nor possible. Second, the HWD
provides unique display capabilities, such as an unlimited field-of-regard. These capabilities may be integral to
emerging NextGen operational concepts, eliminating safety issues which might otherwise constrain the full realization of
NextGen. The paper details recent research results, current HWD technology limitations, and future technology
development needed to realize HWDs as a enabling technology for NextGen.

JAXA (Japan Aerospace Exploration Agency) has been conducting a research project named SAVERH (Situation
Awareness and Visual Enhancer for Rescue Helicopter) with Shimadzu Corporation and NEC from 2008. SAVERH
aims at inventing a method of presenting suitable information to the pilot to support search and rescue missions. An
integrated system comprising an HMD (Helmet-Mounted Display) and a FLIR (Forward Looking Infrared) sensor were
installed in a JAXA research helicopter, and a series of flight tests was conducted to evaluate the benefit of presenting
FLIR images on the HMD in night flight. Three pilots evaluated the display system during six night flights, considering
terrain and position awareness. The tests showed that use of FLIR gave better route tracking performance, and the
effectiveness of head-slaved FLIR on an approach task was shown by subjective pilot rating.

We have presented a new approach for Optical HMT (Head Motion Tracker) past years [1]-[4]. In existing Magnetic HMT,
it is inevitable to conduct pre-mapping in order to obtain sufficient accuracy because of magnetic field's distortion
caused by metallic material around HMT, such as cockpit and helmet. Optical HMT is commonly known as
mapping-free tracker; however, it has some disadvantages on accuracy, stability against sunlight conditions, in terms of
comparison with Magnetic HMT. We had succeeded to develop new HMT system, which can overcome particular
disadvantages by integration with two area cameras, optical markers, image processing techniques and inertial sensors
with simple algorithm in laboratory level environment (2008). We have also reported some experimental results
conducted in flight test, which proved good accuracy even in the sunlight condition (2009). We have also reported some
experimental results conducted in flight test, which proved good performance even in the night flight (2010).
Shimadzu Corp. and JAXA (Japan Aerospace Exploration Agency) are conducting joint research named SAVERH
(Situation Awareness and Visual Enhancer for Rescue Helicopter) [2]-[4] that aims at inventing method of presenting
suitable information to the pilot to support search and rescue missions by helicopters. The HMT system has been
evaluated through a series of flight evaluation in SAVERH and demonstrated the operation concept. In this report, we
show result of the final evaluation of the HMD system through 12 flights including night flight. Also, those evaluation
was done by integrated HMT system that was newly developed for the tests in this year.

Gentex Corporation won the Helmet Mounted Integrated Targeting (HMIT) contract with the Air National Guard
and Air Force Reserve in May 2010 along with Raytheon Technical Services Corporation as the prime contractor.
The HMIT program involves qualification and installation of the Scorpion HMCS Color HMD in both the A-10C
and F-16C Block 30 aircraft types. Qualification tests include all aspects from ejection safety, to NVG and pilot
compatibility as well as performance testing. This paper will review the qualification testing results and program
status along with any lessons learned.

Proc. SPIE 8041, The reported incidence of man-machine interface issues in Army aviators using the Aviator's Night Vision System (ANVIS) in a combat theatre, 80410K (9 June 2011); doi: 10.1117/12.883288

Background: Army Aviators rely on the ANVIS for night operations. Human factors literature notes that the ANVIS
man-machine interface results in reports of visual and spinal complaints. This is the first study that has looked at these
issues in the much harsher combat environment. Last year, the authors reported on the statistically significant (p<0.01)
increased complaints of visual discomfort, degraded visual cues, and incidence of static and dynamic visual illusions in
the combat environment [Proc. SPIE, Vol. 7688, 76880G (2010)]. In this paper we present the findings regarding
increased spinal complaints and other man-machine interface issues found in the combat environment. Methods: A
survey was administered to Aircrew deployed in support of Operation Enduring Freedom (OEF). Results: 82 Aircrew
(representing an aggregate of >89,000 flight hours of which >22,000 were with ANVIS) participated. Analysis
demonstrated high complaints of almost all levels of back and neck pain. Additionally, the use of body armor and other
Aviation Life Support Equipment (ALSE) caused significant ergonomic complaints when used with ANVIS.
Conclusions: ANVIS use in a combat environment resulted in higher and different types of reports of spinal symptoms
and other man-machine interface issues over what was previously reported. Data from this study may be more
operationally relevant than that of the peacetime literature as it is derived from actual combat and not from training
flights, and it may have important implications about making combat predictions based on performance in training
scenarios. Notably, Aircrew remarked that they could not execute the mission without ANVIS and ALSE and accepted
the degraded ergonomic environment.

Military and public safety divers work in a unique and extreme operational environment; characterized by high
turbidity and zero visibility. To help conduct underwater securit and search/recovery missions special sensors are
used. These include imaging sonar, underwater navigation systems, mapping devices, and enhanced underwater
video. A visual display system is the necessary means of providing this sensor information to the diver.
Unfortunately, handheld displays or displays built into the sensor are virtually useless in the environment
characterized by zero visibility.
"Near-to-eye" display systems incorporating micro display technology and its associated optics provide a workable
solution. While a step in the right direction these "near-to-eye" systems - whether developed for commercial or
military applications - have been designed for land-based (or "topside") environments, and fall far short when
simply adapted to a dive mask.
A diver operating underwater with a dive mask in zero visibility presents a unique challenge combining
requirements for small physical size, light weight, large eye-relief (stand-off distance), high data content, and
minimum power.
The following paper describes the successful design of such a system from the perspective of the diver's operating
environment. The resultant system is a light-weight, binocular, mask-mounted visual display that allows for
extended stand-off distance (eye relief), requires no interpupillary or focus adjustments, and provides high data
content color information regardless of ambient visibility conditions.

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